Safety control for machine tools



Jan. 19, 1943. E. D. VANCIL EFAL SAFETY CONTROL FOR MACHINE TOOLS Filed March 9, 1940 2 Sheets-Sheet l IN VEN TOR. [064,4 2 Kara/L J/rr/wop 72 /51:

4 ATTORNEY.

Jan. 19, 1943. E, D VANCIL ETAL 2,308,728

SAFETY CONTROL FOR MACHINE TOOLS Filed March 9; 1940 2 Sheets-Sheet 2 ATTORNEY.

Patented Jan. 19, 1943 SAFETY CONTROL FOR MACHINE TOOLS Edgar D. Vancil and Winthrop Trible, Cincinnati Ohio, assignors to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Application March 9, 1940, Serial No. 323,175

15 Claims.

This invention relates to machine tools and more particularly to safety devices for protecting the cutting tool thereof.

One of the objects of this invention is to provide a machine tool with certain safety features which will reduce inadvertent operating actions that might cause damage to the tool, the work or any of the supports therefor.

Another object of this invention is to prevent the operator from accidentally feeding the cutter into some object other than the Work carried by the work support and thereby causing permanent damage to the cutter or to the object.

A further object of this invention is to provide a safety device which will limit the depth of removable stock that can be fed to a cutter.

An additional object of this invention is to provide a shroud or guard for the tool of a metal working machine which will permit passage of work to the tool but which will prevent any parts which extend beyond the rough surface of the Work, such as parts of a work fixture, from being inadvertently fed into engagement with the cutter.

Still another object of this invention is to provide certain interlocks whereby automatic stopping by a safety device also causes automatic reversal of the transmission thereby preventing the operator from inadvertently restarting the feed in the same direction.

Still another object of this invention is to-provide an improved safety interlock control circuit for a machine tool.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, Without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is a View in elevation of a machine tool embodying the principles of this invention.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a plan View of the work fixture.

Figure 4 is a detail section on the line ii, of Figure 2.

Figure 5 is a detail section on the line 5--5 of Figure 1. I I V Figure 6 is a diagram of the control circuit.

This invention deals with means for improving the safe operation of a machine tool whereby inadvertent relative movements between the cutter and work which might cause damage either to the cutter, the Work, or the fixtures for holding the work may be prevented. Many of these mishaps occur during the process of setting up the machine for an automatic cycle, as for instance, in the case of Where a Work supporting fixture has portions extending above or beyond the rough surface of the work, and miscalculations result in these portions being fed into contact with the cutter. Again, in a productive cycle a work piece may be wrongly placed in a fixture, thereby presenting material for removal by the cutter which is beyond the capacity of the tool, thereby overburdening the cutter as well as spoiling a piece of Work. Again, the feed rate of a machine is determined to a .great extent .on the amount of material to be removed per unit of time and a work piece, although correctly placed, might have an abnormal amount of removable stock on it which would jam the cutter and cause damage either to the cutter or to the working parts of the machine.

With the aid of the safety features of this invention the possibility of these various contingencies happening is greatly reduced.

In principle this invention contemplates providing a metallic shroud or guard around the tool of the machine, insulating the guard from the rest of the machine, and providing an electrical potential between the guard and the remainder of the machine whereby any moving part of the machine, including the work and supporting fixture therefor coming in contact with the guard, will complete an electrical circuit which will auto maticall render the actuating means producing the movement ineffective to continue the movement. Additionally, the reversing mechanism is actuated so that upon restarting the movement will be in a direction to break the contact. This guard is so contrived that it will permit passage of work having a predetermined amount of removable stock thereon to the cutter, but anytures of this invention to best advantage. This ment between the tool and Work is illustrated;

20. By moving lever 56 in the plane of the drawing as shown in Figure 2 the rod 6| will be shifted axially to effect axial movement of the selector valve plunger 20.

By moving lever 56 perpendicular to the plane of the drawing, the shifter rod 6| will be rotated, thereby causing rotation of the selector valve plunger 20. It will now be apparent that the.

operator may preselect the rate and direction of table movement by setting the manual control lever 56, and start and stop the movement of the table by shifting the stop valve plunger '33 by for exemplary purposes, as of the hydraulic type and consists of a hydraulic motor of the piston and cylinder type comprising a cylinder l6, Fig- 7 ure 6, which may be fixed or supported in the bed I5, and a contained piston H which is operatively connected by a piston rod l8 to the table I I for eifecting movement thereof. a

A suitable form of hydraulic control circuit may be provided including a selector valve" l9 having an axially and rotatably movable plunger 28 so drilled and ported that axial movement will change direction, and rotary movement will change rate as from feed vto rapid traverse or vice versa. A feed pump 21 supplies pressure fluid'f'or feeding purposes and is connected in a closed circuit' manner to the selector valve. Thus, the pump has an intake port 22 and a delivery port 23 which are connected by channels 24 and 25 respectively to ports 26 and 21 of the selector valve. When the selector valve plunger is to the right, as shown, port 21 is connected to port 28 and port 26 is connected to port 29 where-- by pressure fluid fiOWS to the stop valve 38 through channel 3| and returns through channel 32.

The stop valve has a plunger 33 in which. is

" formed annular grooves 34 and 35 for separately connected by channels t! 'and l8 to opposite ends of the cylinder l6. It'will now be apparent that the feedpump operates to withdraw fluid from one end of the cylinder and P mp it into the other end of the cylinder to efiect movement. To compensate'for piston differential on the cylinder I! and to provide make-up oil the feed pump has a differential valve 49 connected across it to maintain a suitable pressure diiferential between lines 2% and 25 and insure discharge of excess fluid to reservoir through channel 58, While a booster pump 5i which is supercharged bya rapid traverse pump 52 from the reservoir 53 supplies make-up oil to channel 25 to maintain a suitable operating pressure therein.

The rapid traverse pump 52 is connected by channel 53 to port 54jof the selector valve, and when the .valve is being utilized for feeding purposes this oil is by-passed to reservoir. 7 V I The selector valve plunger 28 may be manually [shifted to its various positions through 'a manual control lever 56 which is supported in themachine 'frame for universal movement byfa ball 51 integral with the lever-as shown in Figure 2.

The lever also has a ball-shaped end 58 fitting in a socket 59in-a crank 60 which is attached to "a shifter. rod 6!. The shifter rod is connected by universally movablelever. 62 to the valve plunger means of the manual control lever 63 which is connected thereto'and pivotally supported at 64. V The lower end of this lever is connected by a link' 65 to an armature 66 of an electric solenoid 61. Energization of this solenoid will shift the stop valve to a stop position.

It may also be desirable to provide for movement of the tool support 12 transversely of the table and this may be accomplished hydraulically nected by channels H and 12 to ports 13 and 14 of the distributor valve 44. The distributor valve may be provided with any suitable means for transferring connections of ports .42 and. 43 from the table motor ports 45 and 46,to ports 14 and 13 respectively. The particular construction of the distributor valve does not constitute any part of this invention and, therefore, the details thereof have not been illustrated herein.

It will be noted,however, that regardless of which slide is being moved by hydraulic pressure that shifting of the stop valve to a stop position will stop whichever slide is moving.

Referringnow to Figure 5, the cutter I3 is surrounded by a flexible, metallicshroud plate 15 which issupported andelectrically insulated from the rest of the machine by an insulating tube 16 which is attached to the quill H. V

The shroud plate 15 is connected to the insulator 16 by suitable screws 18 which pass through elongatedholes in the shroud plate whereby the latter may be adjusted to varythe clearancebetween the end of-the plate and the face of the cutter, this distancebeing indicated by the reference numeral 19. This distance indicates the cross sectional dimension of what may be de-' fined herein as the cutting zone and above this zone is the protective zone. The above-mentioned dimension also indicates the maximum depth of material which may befed' to the cutter for removal thereby; Since the cutting zone lies parallel to the directionof feed of the table it will be obvious that anything carried by the table, whetherwork. or fixture, and projecting through and above this zone will come into con tact with the shroudplate if moved toward the cutter.

The means for creating an electrical potential 8| is wound on one leg of a squarecore and constitutes an exciting coil which sets 'up amagnetic flux which circulates through the lower.

leg 86 and back to the upper leg. The fiux'in the lower leg sets up a potential in a secondary" V coil 81 which may be known as a control cell.

One end 88 of this coil is grounded to the frame of the machine and the other end 89 connected to the shroud plate 15. Although this creates a potential between the shroud plate and the remainder of the machine no current actually flows.

The coil 81 and the leads therefrom to ground and to the plate constitutes a control circuit and when this circuit is closed by contact of some part of the machine with the plate a flow of current starts which produces a countermagnetic flux in the lower bar of the core and diverts the primary magnetic flux to the poles 99 and 9I which reacts on the armature 92 and forcibly draws the armature to the poles. The armature 92 issupported on a suitable pivot 93 and when actuated closes a circuit 94 to a relay coil 95. Energization of the relay coil closes contacts 96 and 91 of an independent circuit 98 to electrical solenoid 61, which as previously explained, has an armature 66 for shifting the stop Valve plunger 33 to a stop position. This circuit is connected to the power mains 83 and 84 through switch 99.

Assuming the work piece I5 and supporting table II moved in the direction of arrow I99 as indicated in Figure 6 to establish contact with the ring I5, the action as explained thus far is that current will flow in coil 81 drawing armature 92, closing the circuit to relay coil 95, closing the circuit to solenoid 61, and thereby shifting the stop valve to a stop position.

Since the Work piece I5 and table really constitute part of the conductor 88, because it is to be understood that the entire machine is constructed of metal, the armature 92 cannot be released until this circuit is broken by moving the work piece I5 out of contact with the ring I5. Furthermore, the solenoid 61 is sufiiciently strong to prevent manual manipulation of the control lever 63 to effect shifting of the stop valve to a running position.

Forcibly overcoming the solenoid to shift the stop valve would be futile because the table would again move in the direction of arrow I creating greater pressure between the work piece I and the ring I5. It should thus be obvious that it is necessary to change the direction of movement of the table and work before it becomes possible to break the contact between the work piece and the ring I5.

A push button IBI has been provided in the circuit 94 for breaking the circuit to relay 95 to effect de-energization of the solenoid 67. To insure that the operator does not operate this button and throw the stop valve lever 63 to a runing position and cause further advance of the work piece toward the cutter, means are provided for automatically changing the position of the reverse valve plunger 20 and regardless of its former position so that when the operator does depress the button I9I and throw the lever 63 to a running position that the work and table will move in a direction opposite to that which caused the contact to be made.

The means for accomplishing this consists of a pair of solenoids I02 and I03 which are uperatively associated with the control lever 56, a selector switch I04, and a pair of relays indicated generally by the reference numerals I95 and I96. The selector switch I94 works opposite to the position of lever 56 and shifter rod 6| in the sense that when the shifter rod is to the left,-as viewed in Figure 6, the solenoid I93 is potentially connected for shifting the rod 6| to the right; and when the rod 6| is in a right hand position the switch potentially connects the 7'5 solenoid I92 for operation to shift the rod to the left.

As shown in Figure 4, the control lever 55 passes through an elongated hole I91 in plate I98 which is operatively connected to armatures I99 and III] of solenoidsI92 and i935. The elongated slot permits up and down movement of the lever 5'6 to effect rat changes. It makes it possible, however, for the plate to shift the lever regardless of its rate position.

The solenoids 92 and I93 are normally deenergized thereby, not interfering with the normal manual operation of the lever.

The relays i and 595 have operating coils Hi and H2 respectively which are connected by a common conductor M3, to circuit 9 5 which, in turn, is connected to the power line 83. The selector switch It l determines which one of these relay coils will be energized when the armature 92 closes circuit 94. The terminal N4 of relay coil MI is connected by conductor M5 toswitch point N9 of the switch I94 and the terminal IIT of relay coil I I2 is connected by conductor I I8 to switch point H5 of switch I94. The switch I94 has a lever $29 which is operatively connected to the collar i2l of the shifter rod 5| and when the shifter rod is to the left the switch lever is positioned to connect point M9 to point I22 and thereby to power main 8 5. Since the switch point H5 is open at this time relay coil I I2 will be deenergized while relay coil EH will be energized. When the shifter rod 6i is in its other position the switch point H5 will be connected to point I23, and thus the power main 82 whereby relay coil H2 will be energized and relay I95 will not be energized.

I With the parts in the position shown, the relay coil HI will be energized and the armature I24 will move upward, as viewed in Figure 6, interconnecting switch contacts 525 and H6 and disconnecting normally closed contacts l2? and I28.

When the circuit is clos :l to line H3, current will flow through normally closed contacts I30 and I3i to relay coil IE3. The other end of the relay is connected through closed contacts. H9 and I22 to power main 99. It will be noted that current does not flow through relay coil I 52 and solenoid I92 because of open contacts I58 and I23. Thus the selector switch determines which relay coil and solenoid will be energized upon closing of armature 92.

The closing of contacts 525 and 525 establishes a holding circuit for relay coil III and solenoid I93 through line I29. This is necessary because as soon as the shifter rod 5! moves, it breaks the connection between contacts IE9 and I22. The holding circuit thus maintains the solenoid IE3 energized until the shifting of rod Si is completed.

The opening of contacts I22 528 prevents energization of solenoid I92 by the closing of contacts H9 and 23 when the shift has been completed. It does not prevent, however, the energizaticn of relay coil H2, the armature I32 of which now operates to close contacts 533, I34 establishing its holding circuit through lines I35 and I29 and opening contacts I39 and ISL breaking the circuit to solenoid I93.

The operator now presses button lilI with one hand and throws lever 63 with the other hand, causing the table to move away from the cutter, which breaks the circuit to the induction relay 89, whereby the armature 92 drops out breaking the circuit to relays i235 and I99. The relays are now restored to their normal position.

plane of the finishedsurfaces of the bosses.

limited portion thereof for work engagement 'whereby a cutting zone and a protective zone work piece l5 has a series of bosses I36 to be machined. The work is secured to the table by hold-down clamps I31 which project above the 5 The path of relative movement is illustrated by the dot and dash line I38. It will be obvious that any miscalculation in making these movements may cause engagement between the cutter and one of the clamps.

frame for relative movement, a cutting tool mounted in said tool support and an actuator for effecting said movement, the combination of a protectbr for said cutter supported adjacent thereto, an electrical circuit having terminals connected to said frame and to said protector, means in said circuit for creating an electrical potential difference between said protector and the remaining parts, of the machine whereby any relative movement effected by said actuator resulting in contact between the protector and any part of the machine will cause current to flow in said circuit, and means in the circuit responsive to said flow of current for rendering said actuator inefiective to cause further movement.

2. In a machine tool having atool support, a work support and means connecting said sup- 7 ports, the combination with a tool mounted on the tool support, of a guard supported in shrouded relation to the tool but exposing a are created, an actuator for propelling one of said supports relative to the other in a direction parallel to said' zones whereby any portion of the work, support or parts carried thereby extending into the protective zone will engage said guard, and means responsive to said engagement to :render said actuator propulsively inefiective.

3. In a machine tool havinga too-l support and I awork support, the combination with a tool mounted on the tool support, of a guard surroundingsaid "tool butproviding a predeter mined clearance to permit passage of work to the cutter, power operable means for feeding the 55 work support and work past the guard to the cutter, electrical control means responsive to contact of any object or portion of an object carried by the work support with said guard to render aid power operable means ineffective to produce further feeding movement. r

4. In a machine tool having a toolsupport and a work support, the combination with a tool mounted in the tool support, of a metallic guard surrounding the tool but electrically insulated 65 'from the machine, an electricalfcontrol'circuit tool mounted on the toolsupport, of a flexible metallic guard supported adjacent to but in:- I

sulated from the cutting tool, power operable means for eifecting relative movement between the supports whereby a. work piece may be fed past the cutter, a. pilot control circuit having one terminal connected to the cutter support and the other to the guard whereby any part being moved by said power operable means and causing de-' fiection of the guard into contact with the cutter support during the feeding movement will close said pilot circuit, and me'ans'actuated by. said pilot circuit for rendering said power (mor able means inefiective. T

6. In a machine tool having a tool support and a work support, the combination with a cutter mounted on the tool support, of a guard supported adjacent said'cutter but electrically insulated therefrom, a'pilot circuit having one terminal electrically connected to the work support and the other terminal electrically connected to the guard, power operable means for f feeding. the work support, and means responsive to closing of thecircuit by contact of the work support or any part carried thereby with said guard for rendering said power operable'means ineffective.

7 In a machine tool, the combination of a cutter support, a cutter mounted thereon, a work whereby any object carried by the supports and contacting said means will close said circuit, actuating means for effecting relative movement between the supports, and means responsive to i closing of said circuit'for disabling said actuating means.

I 8. In a machine tool having a cutter support and a work support and a cutter mounted on said cutter support, the combination with means for effecting 'a relative feeding movement between said supports, of a guard surrounding said cutter and spaced a predetermined distance therefrom, said guard being of flexible metallic material, means insulating said guard from its support, an electrical control circuit having oneterminal'attached to said guard and the, other terminal electrically connected to said supports whereby'any deflection of the guard during relative movement between said supports byany part carried there-' by will close said circuit, means responsive to closure of said circuit to stop the moving. sup-' port, said guard being spaced a sufficient distance to permit overrun of the moving supportwithout interference between the guard and the cutter.

9. In a machine tool having a tool carrier and a work carrier and unitary means for supporting said carriers, the combination with a tool mounted on the tool carrier, of a guard supported'in shrouded relation to thetool but exposing a limited portion thereof for work passage whereby, a cutting zone and a protective zone are created,

an actuator for; propelling one of said carriers toward the other whereby any portion of the ing in the protective zone will collide with said guard, and means responsive to said collision l to render said actuator propulsively ineffective:

10, In a milling machine havinga rotary' cutter and a support therefor, the combination of a shroud plate surrounding said cutter, means for feeding work past said plate to the cutter, means for creating an electrical potential between the cutter and the plate including a control circuit, said plate being flexible whereby any bending of the plate during operation of the actuator will close said circuit and means responsive to the closing of said circuit to render said actuator ineffective.

11. In a milling machine having a rotary cutter, a support therefor, and a work support, the combination of a shroud plate for said cutter, an actuator for feeding the work support and work carried thereby past the cutter, means for adjusting said plate for determining the maximum thickness of material to be removed by the cutter, means to create an electrical potential between the plate and work whereby a work piece having removable material exceeding said maximum depth will engage said plate and close said circuit, and electrical responsive means in said circuit i or disabling said actuator.

12. In a milling machine having a cutter support, a rotary cutter mounted thereon and a work support, the combination of a source of power, motion transmitting means coupling said source of power for relative movement between said supports, said motion transmitting means including reversing means and stop means, a protecting guard for said cutter, means to create an electrical potential between said guard and said supports including a control circuit, and means in said circuit responsive to energizatio-n thereof to actuate said stop means and said reversing means whereby the source of power is disconnected from the moving support and the reversing means is preset for a new direction of movement.

13. In a milling machine having a work support, a tool support and a cutting tool mounted on the tool support, the combination with means for effecting relative movement between the supports including reversing means, of a protector for said cutter, said protector having an electrical protential difference with respect to the remainder of the machine and means responsive to a grounding contact with said protector for actuating said reversing means.

14. In a milling machine having a work support, a tool support and a cutting tool mounted on the tool support, the combination with power operable means for effecting relative movement between the supports including reversing means and stop means, of a protector for said cutting tool, means for creating an electrical potential between said protector and the machine, and means responsive to any grounding of the protector with the machine for simultaneously actuating said reversing means and said stop means.

15. In a machine tool having a tool support, a tool mounted thereon, and a work support, the combination of a source of power, means coupling said source of power for relative movement between said supports including reversing means and stop means, a protective guard for said tool, a control circuit terminating in said guard and said supports respectively, means in said circuit to create an electrical potential between the guard and supports, a solenoid for operating said reversing means, a pilot relay therefor, a relay operable upon closing of said control circuit to energize said pilot relay and thereby efiect operation of said solenoid, said reversing means including a two-position control lever, separate solenoids for shifting said lever to its respective positions, control relays for each solenoid, means connecting said control relays in parallel with said pilot relay including a selector switch operable by said lever whereby only one of said relays is connected in parallel with said pilot relay for simultaneous operation therewith, said selection being such that the lever is always operated upon energization of the control circuit, and manually operable switch means in the pilot relay control circuit for opening said circuit to permit manual operation of the solenoid operated stop means.

EDGAR D. VANCIL. WINTHROP TRIBLE. 

